I assume it will be harmful to the baby if a woman smokes while pregnant. How about the situation where the woman smokes, gets pregnant and then stops? Does the smoking in the period until the pregnancy affect the baby? How long before a pregnancy does a woman need to quit smoking in order to insulate the baby from the negative effects of smoking?

  • I guess there are a lot of articles on the internet, which actually refer to scientific journals.
    – Ooker
    Oct 1, 2015 at 14:28
  • You might be interested in this related question about smoking during pregnancy.
    – michaelpri
    Oct 1, 2015 at 23:49
  • @michaelpri I saw the question before posting, but I am specifically interested in the period up to the pregnancy. Nevertheless, thank you. Oct 3, 2015 at 12:48
  • In your subject and one part of your question you ask about quitting smoking before pregnancy, in another part you ask about stopping after finding out about the pregnancy. My sources say it makes no difference (see my answer), but those are still different questions
    – YviDe
    Oct 18, 2015 at 9:51

1 Answer 1


While most studies appear to be on women who quit during pregnancy, I found a study that compared pregnancy outcomes in women who never smoked, quit smoking before pregnancy, quit smoking in early pregnancy, and those that smoked during pregnancy. It found

maternal smoking cessation before or during early pregnancy appears to result in appropriate fetal and childhood growth

The whole study Active and passive maternal smoking during pregnancy and the risks of low birthweight and preterm birth: the Generation R Study is available on the internet and I recommend reading it in full and also looking at the references. The differences in birth weight between the babies born to women who quit before and during early pregnancy were not significant.

Another study in 7000 women in the Netherlands also found no difference between women who didn't smoke and women who quit before 18 weeks of pregnancy.

For all active smoking categories in early pregnancy, quitting smoking was associated with a higher birthweight than continuing to smoke. Tendencies towards smaller non-significant beneficial effects on mean birthweight were found for reducing the number of cigarettes without quitting completely. This study shows that active and passive smoking in late pregnancy are associated with adverse effects on weight and gestational age at birth. Smoking in early pregnancy only, seems not to affect fetal growth adversely.

Active and passive maternal smoking during pregnancy and the risks of low birthweight and preterm birth: the Generation R Study

Note that for all of these studies, just reducing the number of cigarettes per day is counted as continuing to smoke.

  • This is a very good answer, thank you. Oct 18, 2015 at 18:42

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